Through Hull Replacement, Part 4: Resizing the Holes

Chamfering the New Hole with the Dremel

Having settled on Groco brand through-hulls to replace the original through-hulls, and having prepped the original holes by removing the deteriorated plastic liners, the next step I needed to take was the resizing of the original holes. This was not an easy task, at least at first, but it did get easier as I moved along from one hole to the next and taught myself the techniques that were necessary for doing this job correctly and efficiently. There were no printed resources or illustrated Internet sources that taught me how to do this. Like so many other projects and sub-projects in this refitting of Oystercatcher, my Ericson 25, this little project required its fair share of trials and errors and, I might add, more than one glass of Dionysus to help me think through the various steps along the way.

The new through-hull seated within the old hole

There were some people on some Internet forums who said that they had resized their old holes with thickened epoxy by using the new through-hulls as molds of sorts for the new hole. Not sure what I'm talking about? Just look at the picture above. Now picture some thickened epoxy in that gap around the head of the new through-hull. The idea is that you use the new through-hull to shape the thickened epoxy around the lip of the original hole.

These various people on the Internet forums said that by greasing or waxing their through-hulls they were able to prevent the thickened epoxy from sticking to them. This, of course, would be something everyone would want to avoid, right? I mean . . . only the most dimly-lit of all boat owners would want to permanently bond his new through-hulls to the hull with epoxy.

I followed these Internet voices of advice, but only to a certain point, as I shall explain. One piece of advice that I obviously followed was to use wax to prevent the epoxy from grabbing the bare bronze of the through-hull. I did not go out and drop a wad of money on mold release wax or some such thing from West Marine. I just used plain old carnauba wax. Where did I get it? The local hardware store. Why did I trust this inexpensive carnauba wax over mold release wax? A local boatyard owner provided me with this advice.

After I had finished smearing the through-hulls with wax, I mixed up some epoxy and soaked the fiberglass in and around each of the holes.

This soaking of the fiberglass would of course seal it up and thus help to prevent the blistering of the fiberglass in the event that the sealant I would use in this area failed.

The soaking of the fiberglass would also help the thickened epoxy bond to the hull.

Below we see the galley sink drain hole. As I said in the previous posting, this was not an easy hole to work on due to the proximity of the hole to the bunk of the trailer.

Having soaked all three holes, my next move was to thicken-up this neat epoxy with some colloidal silica.

I thickened it to the consistency of peanut butter.

Then I started daubing it around the edges of the hole. This first hole that I tackled was the .75 inch raw water intake hole for the head. I figured it would be better to start with this hole than the larger 1.25 inch waste outlet hole.

I overloaded the hole with epoxy, so that there would be plenty of squeeze around the edges when I inserted the new through-hull.

Satisfied with the amount of epoxy in the hole, I grabbed the new, wax-coated through-hull and placed it on my ring finger.

After I had fully inserted the new through-hull, I sat back and observed it closely. I was not satisfied with the squeeze. As you can see in the photo below, there's not much at all. This worried me, so I pulled the through-hull back out and daubed some more thickened epoxy into the hole.

Then, I reinserted the through-hull into the hole.

I allowed the through-hull to sit for a short while. I wanted the epoxy to warm up and begin to kick, but I didn't want it to go too far while the through-hull was still inserted into the hole. This removal of the through-hull on my part was my point of departure with some of the advice that I had read from various persons on various forums. Some of these persons had said that in order to resize a hole, one should allow the through-hull to remain in place throughout the epoxy-curing process. A waxed nut or seacock on the interior of the boat would allow the through-hull to be fully seated in the hole and would allow the through-hull and other hardware to be removed after the epoxy had cured. This was what they said. Perhaps some of these persons had in fact resized their holes in this fashion, but without any pictures or thorough descriptions of how exactly they were able to accomplish this without having any of the epoxy bond to any of this hardware, I could only trust my own experience with epoxy. From my standpoint, I could not imagine how I could perform this thoroughly messy task without getting at least some of the epoxy in some places where it didn't belong. Therefore, I opted to remove the through-hull after it had sat for some time (but before it had fully kicked).

This approach worked reasonably well. Although the streaks of epoxy here and there on the hull did not look especially attractive, the impression left by the through-hull in the hole itself was quite clean. I wasn't worried about the ugly mess on the hull. This I simply planned to sand away after the epoxy fully cured.

After I was finished making the impression, I wasted no time trying to clean all the epoxy off of the through-hull. I started with vinegar, the cleaning agent that I normally use in place of acetone. If you've never used it, you ought to give it a try. It's a lot cheaper than acetone and much safer. My vinegar of choice, before its unfortunate demise, was that high quality stuff from Piggy Wiggly, or "The Pig," as everyone around the Carolina Lowcountry used to call it.

The vinegar, despite coming from The Pig, was not high-powered enough to remove both the epoxy and the wax.

Therefore, I had no choice but to pull out the tough stuff - toluene - that solvent that makes acetone seem like kid's play.

A short soak in a pickle jar full of toluene, and the through-hull was far cleaner than it had been when I started this job.

At this point I transitioned to the 1.25 inch waste outlet hole. From what I could determine, this hole did not need to be filled with thickened epoxy. It seemed that the head of the flush-mounted through-hull would fit into the chamfered area of this hole just right. I emphasize the word seem here, because I would later discover that this hole in fact would need a little bit of thickened epoxy. I will address the filling of this hole in a subsequent posting in this series. At this time, I simply recoated the fiberglass in the hole for the purpose of fully saturating it and thus protecting it.

Having completed the 1.25 inch hole, I moved down to the galley sink drain hole. Hitting that hole again with neat epoxy for the purpose of again saturating the fiberglass, I then thickened up the epoxy with some colloidal silica in preparation for filling the hole.

My young helper, back from the house, snapped a few pictures of my work on this difficult-to-access hole.

The impression left in this hole was not quite as clean as the one that was left in the first .75 inch hole. At the time, I blamed it on the awkward angle at which I was working. Whether it was this, or it was simply my weariness at this late point in the day, I'm not sure.

Several days later I returned to this job site and got to work sanding away the excess epoxy on the hull. I started with the raw water intake hole. I began by trying to sand the hull with a large sanding block. I had constructed this block sander for a different project out of a 2x4 and a piece of paper intended for drum sanders. It didn't work very well on account of the curvature of the hull.

Next I grabbed a small rubber sanding block and loaded it with 40 grit paper. This is the type of paper that I had used many other times for sanding fully-cured epoxy. As I've said in other postings, sanding fully-cured epoxy that has been thickened with colloidal silica is about like sanding concrete. Without 40 grit paper it's difficult to make much progress.

I took my time with this sanding. The last thing I wanted to do was to sand all the way through the bottom paint.

The epoxy remained a stubborn opponent to the very end.

Despite my patience and caution, I still ended up sanding through the bottom paint in one spot. This spot would need to be soaked in epoxy before it came time to bottom coat this area again.

The hole didn't look so bad at this point. The task before me now was to carefully sand the chamfered area around the hole, so that the head of the through-hull would fit snugly into place.

Given the ruggedness of the fully-cured epoxy, I knew that hand-sanding would be out of the question. For this job I turned to my Dremel and its right-angle attachment. The right-angle attachment was a necessity, since the bunk of the trailer was so close. I thought that the bullet-shaped grinding bit would be the best bit for the job. It wasn't.

The bullet-shaped grinding bit was too rough and too difficult to control. I began to worry that it would leave divots and other inconsistencies in the epoxy.

I soon replaced the bullet-shaped grinding bit with a small sanding drum loaded with a 50 grit wheel.

This little drum sander did an outstanding job.

After I had smoothed out the rough areas within the chamfered area around the hole, I inserted the bronze through-hull. As you can see, at this point I still needed to remove a good bit of epoxy, if I wanted the head of the through-hull to be fully seated within the hull.

This time, it fit just right.

I ended this part of the project by spending about five minutes running some 40 grit paper around the chamfered area in an effort to give the hole even greater consistency.

The raw water intake hole for the head, as you see above, turned out just right. The galley sink drain hole, on the other hand, did not. I monitored the epoxy in this hole for an entire week after I had daubed it into place. It never hardened up. Instead, it exhibited a spongy consistency. I had never had this happen with MAS epoxy or with RAKA epoxy, the latter of which I had used for this job. All I can figure is that somehow I had gotten the 2-1 ratio of resin-to-hardener screwed up. You might recall that this was the last hole that I filled, and that it was the end of the day when I did it. Whatever the case might have been, I knew I needed to remove this stuff and start over. I thought this would be difficult to remove, but it was actually quite easy. The chisel easily cut through this spongy material.

After I removed the first chunk of this spongy epoxy from the hole, I put it on the frame of the trailer. I was able to slice through this chunk with the tip of the chisel with ease.

After I had prepped the hole once again with neat epoxy, I daubed it once again with thickened epoxy.

The hole as it appeared soon after I had impressed the epoxy with the bronze through-hull.

Several days later, after the epoxy had full cured, I loaded up the quarter-sheet sander with 40 grit paper and went to work.

The hole was too close to the bunk of the trailer for hand-sanding to be very helpful.

Feeling bold, I went so far as to use the angle grinder on the stubborn epoxy on the hull.

Somehow I managed to remove almost all of the epoxy with the grinder without damaging the bottom paint.

I cleaned up the hull and the hole with toluene.

Then, just as was the case with the first .75 inch hole, I grabbed the Dremel and got to work smoothing up the chamfered area of the hole.

After some careful sanding, I tested the fit of the bronze through-hull. Unfortunately, I discovered that this hole needed just a little more epoxy in some areas.

Therefore, I reluctantly mixed up some more epoxy, thickened it with colloidal silica, and daubed the hole once again, albeit more modestly.

Several days later, I came back and hit this hole once again with the Dremel. Now, at last, this hole was offering a snug fit to the new bronze through-hull.

This resizing of the holes ended up taking more time than I had originally expected. Nevertheless, I knew that I had done this job correctly, and I could now move on to the next part of this multi-part project - the construction and installation of the backing plates for the interior of the hull.

This ends this posting on how I resized the original holes for the new bronze through-hulls on Oystercatcher, my Ericson 25.